ComScore’s Mobile Year in Review report shows the U.S. trails Italy, Spain and the United Kingdom by measure of smartphone adoption rate. In Spain, for example, 38 percent of people have smartphones compared with 27 percent in the U.S. Still, smartphones have exploded in popularity over the past year. The smartphone penetration rate in the U.S. rose a full 10 percentage points in the year.

Cisco recently estimated the amount of mobile data traffic for the year exceeded the entire Internet’s in 2000. That should only accelerate in 2011, as more consumers trade in so-called feature phones for iPhones and advanced phones running Google’s Android operating system. By some estimates, the number of smartphone users will surpass feature phone users this year.